Antioxidant power of angiotensin-converting enzyme inhibitors in vitro

Aims There is controversy regarding the potential antioxidant effect of captopril, therefore this study was performed to compare the in vitro antioxidant power of captopril with other angiotensin-converting enzyme (ACE) inhibitors.
Methods Antioxidant power of captopril, enalapril, fosinopril, perindopril, quinapril and ramipril in aqueous solution was measured using the ferric reducing (antioxidant) power (FRAP) assay; captopril was also measured in ethanolic solution.
Results Only captopril showed significant antioxidant power, demonstrating a stoichiometric factor of 1.0 in this assay. Concentration-related antioxidant power was seen in both aqueous and ethanolic solutions.
Conclusions Captopril shows antioxidant activity in vitro . This property could be relevant in vivo if captopril is concentrated in membranes, lipoproteins or at other important sites.